PhotosPhotos: Syrians React to Reported Gas Attack08.21.13PhotosPhotos: Syrians React to Reported Gas AttackActivists say the government killed hundreds of people on Wednesday by firing rockets filled with poisonous gas into Damascus. See photos from inside the shocked capital.08.21.13 4:16 PM ETHassan Ammar/AP,Hassan AmmarTwo Syrian rebel groups claim that government forces used nerve gas in Damascus on Wednesday, reportedly killing hundreds. Activists claimed that up to 600 people had been killed in the attack, and hundreds more were reportedly wounded. The two groups said that rockets filled with poisonous gas were fired into the capital, and amateur video found online showed victims sprawled out on hospital floors, with others being treated with hand-pump respirators. The government of President Bashar al-Assad denied using chemical weapons, calling the claims “baseless” on state-run television. The attack comes just one day after chemical weapons experts were sent to Damascus by the United Nations to investigate the government’s alleged use of nerve gas. Pictured: Syrian military soldiers check identifications at a checkpoint on Baghdad Street, in Damascus Wednesday. Ammar Dar/Reuters,STRINGERA man, affected by what activists say is nerve gas, breathes through an oxygen mask in the Damascus suburbs of Jesreen. Bassam Khabieh/Reuters, via Landov,STRINGERSome of the victims were in the Duma neighborhood of Damascus. Syrian activists said that many women and children were killed as a result of the airstrike. Bassam Khabieh/Reuters,STRINGERIf confirmed, Wednesday's attack would be by far the worst reported use of chemical arms in the two-year-old civil war. Exactly a year ago, President Obama warned that the confirmed use of chemical weapons in Syria would mark the crossing of a "red line." Mohamed Abdullah/Reuters,STRINGERA woman—sickened by what activists say is a gas attack—vomits as she takes shelter with other civilians inside a mosque in the Duma neighborhood of Damascus. Mohamed Abdullah/Reuters,STRINGERThe Syrian armed forces strongly denied using chemical weapons. Syrian state television said the accusations were fabricated to distract a team of U.N. chemical weapons experts who arrived three days ago. Mohamed Abdullah/Reuters,STRINGERGirls rest inside a mosque in the Duma neighbourhood of Damascus. Mohamed al-Abdullah/Shaam News Network, via Reuters,HANDOUTRelatives and activists inspect the bodies of people they say were killed by nerve gas in the Ghouta region, in the Duma neighbourhood of Damascus.